Adipogenesis is a process to differentiate preadipocytes into mature adipocytes and accumulate lipids in cytoplasmic organells named of lipid droplets, which is known to be a risky factor which may give rise to various adult diseases such as obesity, diabetes, steatosis and coronary heart disease. Precursor fat cells such as fibroblasts can be differentiated into mature ones resulting in the formation of lipid droplets within them. The differentiation mechanism has been studied by using specific cell lines such as 3T3-L1. Adipocyte differentiation is a complex process accompanied by coordinated changes in morphology, hormone sensitivity, and gene expression. These changes are regulated by several transcription factors such as C/EBPs (CAAT enhancer binding proteins), PPARs (Peroxisome Proliferator-Activated receptors), and ADD/SREBPs (Adipocyte determination and differentiation dependent factor 1/sterol regulatory element-binding proteins). (Bart A Jessen et al., Gene, 299, pp 95-100, 2002; Darington et al., J. Biol. Chem., 273, pp 30057-30060, 1998; Brun R. P et al., Curr. Opin. Cell. Biol., 8, pp 826-832, 1996). These transcription factors are induced at different stages of adipocyte differentiation and functionally interact with each other to conduct adipogenesis and lipogenesis by regulating gene expression. For example, C/EBP β and δ factors are temporally overexpressed by the external hormonal stimuli such as MDI (isobutylmethylxanthin, dexamethason and insulin), which triggers adipocyte differentiation process. (Reusch J. E. et al., Mol. Cell. Biol., 20, pp 1008-1020, 2000). Subsequently, they induce the increase of C/EBP α and PPAR γ (James M. N. et al., J. Nutr., 130, pp 3122S-3126S, 2000). Especially, PPAR γ is predominantly expressed in adipocytes and is a key determination transcription factor for adipogenesis, which forms a heterodimer with RXR (Retinoic acid X receptor) and binds to PPRE (Peroxisome Proliferator Response elements) found in promoters of various genes involved in adipogenesis (Tontonoz P. E. et al., Genes Dev., 8, pp 1224-1234, 1994). The interaction between C/EBP α and PPAR γ is crucial in the adipocyte differentiation and those factors control the expression of adipocyte-specific genes such as fatty acid bound protein, aP2 and lipid metabolic enzymes. Especially, ADD1/SREBPs also plays a key role for lipogenesis and insulin-stimulated gene expression, and the expression of ADD 1/SREBP1c contributes to the activation of PPAR γ (Rosen E. D. et al., Annu. Rev. Cell Dev. Biol., 16, pp 145-171, 2000; Osborn T. F., J. Biol. Chem., 275, pp 32379-32382, 2000). The adipocytes finished the differentiation process synthesize lipids and store them in a form of triglycerides.
In the meanwhile, the homeostasis of lipid metabolism is maintained by the balance between synthesis and disintegration of fat. ADD1/SREBP1 controls the synthesis of fatty acid, triglyceride, cholesterol, and phospholipid etc (Horton J. D. et al., J. Clin. Invest., 109, pp 1125-1131, 2002). SREBPs are synthesized as about 1150 amino acid precursors bound to the endoplasmic reticulum and nuclear envelope. To be active, the membrane-bound SREBP must be ptoteloytically cleaved to release the N-terminal segment so that it can enter the nucleus. The cleaved SREBPs, designated the nuclear form, binds to the SRE (sterol regulated elements) in the regulatory gene promoter. The genes regulated by SREBPlc, one of the SREBP isoforms are ACL (ATP citrate lyase), ACC (Acetyl CoA Carboxylase), FAS (Fatty acid synthase), and SCD (Stearoly-CoA desarurase) etc (Osborn T. F. et al., J. Biol. Chem., 275, pp 32379-32382, 2000; Soazig L. L. et al., J. Biol. Chem., 277, pp 35625-35634, 2002). It has been reported that PPAR α plays an important role in regulating lipolysis (Beisiegel U., Proc. Natl. Acad. Sci. U.S.A., 96, pp 13656-13661, 1999) through control of lipid metabolic enzymes such as LPL (lipoprotein lipase), apoproteins, ACO (Acyl-CoA oxidase), thiolase (Dreyer C et al., Cell, 68, pp 879-887, 1992).
Obesity results from a chronic imbalance between energy intake and energy expenditure, resulting in increased fat storage. The mechanism of obesity is not fully understood however, the complex interactions of neural, hormonal, genetic and environmental factors due to Westernized diet are thought to induce this obesity epidemic. Over accumulation of fat might be a high risk factor for various metabolic syndromes such as diabetes, hypertension, dyslipidaemia and cardiovascular disease. (Manson et al., New England J. Med., 333, pp 677-685, 1995; Kopleman P. G., Nature, 404 pp 635-643, 2000; Must et al., JAMA 282, pp 1523-1529. 1999).
Although there are several well-known representative anti-obesity agents such as Xenical™ (Roche Pharm. Co Ltd. Swiss), Reductil™ (Abbot Co Ltd. USA) and Exolise™ (Atopharma Co Ltd. France), more effective agents have been needed because of their side effects such as heart disease, respiratory disease and neuronal system disorder.
Recent strategies for developing anti-obesity agent are focused on reducing diet, inhibiting calorie intake, stimulating thermogenic reaction, regulating energy metabolism, and controlling signal transduction through neuronal nerve system (Kopleman P. G., Nature, 404 pp 635-643, 2000). There have been many attempts to develop effective anti-obesity agents, however satisfactory drugs showing potent efficacy as well as safety have not been developed yet.
Accordingly, the attempts to develop an effective anti-obesity agent with natural products of which safety has been verified are more effective rather than them with synthetic substance.
Most of the plants belonged to Cucurbitaceae family of Dicotyledonaceae class are annual or perrenial viny plants and distributed in tropical and subtropical zone. Among them, Melothris japonica, Schzopepon bryoniaefolius, Gynostemma pentaphyllum and the like have been distributed, and pumpkin (Cucurbita moschata DUCH), water melon (Citrullus vulgaris SCHRAD), sponge gourd (Luffa cylindrical L. ROEM), cucumber (Cucumis sativus L) and the like have been cultivated in Korea.
It has been reported that pumpkin (Cucurbita moschata DUCH) comprising cucurbitine and fat oils such as linoleic acid, oleic acid, carotene etc shows anthelmintic activity; water melon (Citrullus vulgaris SCHRAD) comprising citrulline, alanine, fructose, glucose etc shows potent diuretic activity; sponge gourd (Luffa cylindrical L. ROEM) is used as a washing tool; and cucumber (Cucumis sativus L) comprising glycoside, caffeic acid, cucurbitacins etc shows diuretic activity according to the literature (Chung B. S et al: HyangyakDaesajeon, young-rim press, pp 945-957, 1998).
However, there has been not reported or disclosed on the preventing or treating activity of the alcohol compound isolated from the extract of Cucurbitaceae family plant showing potent anti-obesity effects in any of above cited literatures, and the disclosures of which are incorporated herein by reference.
To investigate the anti-obesity effect of the alcohol compound isolated from the extract of Cucurbitaceae family plant, the inventors of present invention have intensively carried out various in vitro experiments testing the inhibitory effects on adipocyte differentiation and triglyceride synthesis. And also the inventors investigated the activity of this extracts to activate transcription factor, PPAR α regulating the expression of genes involved in adipocytes differentiation. This extracts showed no toxicity in animal test and reduced the body weight of test animals. As a result of these investigations, the inventors finally completed the present invention by confirming that the alcohol compound isolated from the extract of Cucurbitaceae family strongly inhibited the adipocyte differentiation and reduced the body weight of animals. These results suggested that this compound had the potential to be an effective anti-obesity agent.